Black Box LE2700A, User Manual, Page: 33 / 154

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Page 33
Chapter 4: Redundancy
4.4.3 CIST
With the ability to cross regional boundaries, CIST is used by MSTP to communicate with other MSTP regions and with any RSTP
and STP single-instance spanning trees in the network. Any boundary port, that is, if it is connected to another region, will auto-
matically belongs solely to CIST, even if it is assigned to an MSTI. All VLANs that are not members of particular MSTIs are mem-
bers of the CIST.
Port Settings
Figure 4-9. Port settings screen.
Table 4-11. Port Settings screen options.
Label Description
Port The switch port number to which the following settings will be applied.
STP Enabled Check to enable STP for the port.
Path Cost Configures the path cost incurred by the port. Auto will set the path cost according to the physical
link speed by using the 802.1D-recommended values. Specific allows you to enter a user-defined
value. The path cost is used when establishing an active topology for the network. Lower path cost
ports are chosen as forwarding ports in favor of higher path cost ports. The range of valid values is 1
to 200000000.
Priority Configures the priority for ports having identical port costs. (See above).
OpenEdge (setate
flag) A flag indicating whether the port is connected directly to edge devices or not (no bridges attached).
Transiting to the forwarding state is faster for edge ports (operEdge set to true) than other ports.
AdminEdge Configures the operEdge flag to start as set or cleared.(the initial operEdge state when a port is
initialized).
AutoEdge Check to enable the bridge to detect edges at the bridge port automatically. This allows operEdge to
be derived from whether BPDUs are received on the port or not.
Restricted Role When enabled, the port will not be selected as root port for CIST or any MSTI, even if it has the best
spanning tree priority vector. Such a port will be selected as an alternate port after the root port has
been selected. If set, spanning trees will lose connectivity. It can be set by a network administrator to
prevent bridges outside a core region of the network from influencing the active spanning tree topol-
ogy because those bridges are not under the full control of the administrator. This feature is also
known as Root Guard.